The purpose of the present invention is to increase the efficiency of centrifugal decorticators capable of ejecting a stream of grains to collide against an impact surface.
Specifically, the present invention covers improvements in machinery capable of prying open the hulls of grains to which sufficient kinetic energy has been transmitted for impact against a conveniently positioned surface.
To more specifically clarify the purpose of the present invention, mention shall be made of what is meant by "Grain" throughout this description. Grain is a vegetable body comprising a soft central part identified as Kernel, enclosed by a hard covering, usually identified as Hull.
In this description, mention shall be made of the problems appearing in the Sunflower (Helianthus annuus) oil milling industry. Nevertheless, it should be understood that the present invention could be applied to the decortication of other oil grains, such as Safflower, Soya, etc.
Decortication is the action of separating the Hulls from the Kernels, prior to milling and extracting the Oil from the Kernels.
In particular, the present invention is directed to but is in no way limited to the decortication of Sunflower grains, or other grains.
Sunflower grains have an approximate average weight of 0.07 grams; of this weight, approximately 70% corresponds to the Kernel.
In the oil grain industry, particularly in Sunflower oil milling, two high value commercial products are obtained:
The Oil, extracted from the Kernel, and
The solid part of the Kernel, after extraction of the Oil, which constitutes an excellent component of balanced feeds. (This solid part is usually called Meal in the milling industry.)
The Oil and the Meal are obtained from the Kernel, whereas the Hulls show negative qualities, not only from a nutritional standpoint, but also because of their detrimental influence as regards the milling capacity of an oil factory.
In particular, Hulls occupy great volumes of the oil producing machinery, reducing the amount of Kernels which can be milled and the production of Oil (Meal is considered a by-product). The presence of Hulls is the limiting factor in the production capacity of a given oil mill.
Obviously, the ideal solution would be to achieve a total elimination of the Hulls; the product to be milled would then be entirely composed of Kernels.
Sunflower grains have previously been milled with inefficient decorticating systems, or even by direct extraction, with no decortication of the grains.
When milling with this last mentioned method, efficiency is very low; also, the quality of the extracted Oil and of the Meal are particularly inferior.
Also known are equipment that, by means of a particularly violent mechanical action, do crack the Hulls, but simultaneously break the Kernels; so, from this known machinery there emerges a mixture of Kernels and Hulls of diverse granulometry. Also, this known equipment, by the violent mechanical action, causes bits and pieces of Kernel to remain adhered to the separated Hulls. The Hulls--with adhered Kernel fractions--are usually burnt as fuel (or sold at a very small price for other general uses). The Oil and Meal contained in the fractions of adhered Kernels, thus constitute a total loss.
It is interesting to note that a Sunflower decorticator processing 100 metric tons/24 hours (a normal capacity) must attend to one million grains per minute. In a way, these conditions explain the inherent difficulty in achieving the ideal circumstance of totally de-hulling the grains and further separating pure Kernels from totally clean Hulls.
Presently, because of the above-mentioned circumstances, oil mills generally content themselves with milling Kernels in a mix with some 14-19% Hulls.
The above circumstances imply, among other disadvantages, a deterioration of the quality, both of the Oil and the Meal. Hulls include a small percentage of wax which, in the milling process, melts and is incorporated into the Oil. This wax must be later eliminated, as it clouds the Oil, impairing its value. A process for unclouding the Oil is denominated "winterization".
The quality of the Meal is damaged mostly by the Hull presence. Protein percentage decreases drastically (Hulls contain only about 2% protein, which unfavorably averages out with the very high protein content of the solid part of the Kernels); also, Hulls contain about 60% Fiber, making the Meal inadequate for, among others, chicken balanced diets. Hulls also contain Lignine, a definite antidigestion substance.
Naturally, the above-mentioned quality-damaging characteristics of Hull presence increases in proportion to the weight of the Oil shedded along the extraction process. For example, a 15% Hull presence in the Kernels to be milled can well increase to a 26% presence in the Meal, due to the loss of the weight of the Oil.
The above-described impossibility of obtaining a clear Oil and a Meal of a good enough quality to make a reasonable profit has induced a number of mills to adopt the so called "integral" milling method, abandoning inefficient decorticating as not worth their while. Such "integral" milling--commercial reasons apart--causes a tremendous drop in the quality of the products, especially the Meal. In these cases, Kernels enter the milling process mixed with at least 25-30% Hulls; the corresponding Meal will have over 40% Hulls. The consequence of the above is that a very high percentage of Fiber and also of Lignine (and the resulting very low Protein) transform a first class foodstuff into an extremely low grade feed.
Once the grain has been decorticated, the mixture of Kernels with the least possible percentage of Hulls is passed through presses which extract a high percentage of the Oil; the material emerging from the presses (known as Cake) contains about 15% Oil. This Cake then proceeds to solvent (hexane) extractors from which the Meal emerges, which is then commercialized including about 1.5% Oil and 12% humidity.
As described previously, it is evident that a smaller percentage of Hulls--entering the presses mixed with the Kernels (ideally 0%)--would bring about the following most important advantages:
A purer Oil, with less wax content.
A Meal having a high Protein content and a low Fiber and Lignine content, with excellent nutritive value.
An enlargement of the milling capacity for a given oil factory due to the elimination of Hulls (low specific weight-high specific volume) and their replacement by Kernels (high specific weight-low specific volume). Such an increase in milling capacity is achieved with no alteration in production costs; it is a true saving.
A previous excellent design is a Decorticating machine corresponding to the Argentine Patent No. 201397, of the same inventor, which Patent is incorporated together with the present description as added documentation, to better clarify the scope of the present invention.
This known Decorticating machine allows a range of some 14-19% Hulls accompanying Kernels in the mix going to presses and extractor. This design complies with accepted international standards. It consists of a grain distributor placed over a spinning rotor with radial blades disposed around a nucleus which orientates discharge, the rotor is surrounded by an annular Impact Band, which faces the rotor's discharge. Between the Impact Band and the rotor's discharge, there is defined an annular opening for discharge of the decorticated material, which decorticated material enters a Hull separator, generally pneumatic; this Hull separator does not fall within the scope of the present invention.
Grains are ejected from the rotor, by centrifugal action, and against the mentioned impact band; the grains are broken by the resulting concussions. This Decorticator corresponding to Patent No. 201397, as well as the other decorticators known in the art, do not solve the problem of the grains adopting diverse positions within the rotor and, consequently, hitting the impact band at diverse positions and angles.
In analyzing oil grains--especially Sunflower grains--it is observed they present a flattened shape; their Hulls are defined by two shell-shaped and substantially symmetrical parts, joined at the edges and their material is composed of cellulosic fibers, joined by lignine. Their physical build-up makes them particularly resistant and resilient such that they strongly oppose the decorticating action.
Nevertheless, it is known that, if it is possible to achieve an impact of said grains at high speed against a solid surface, and the impact happens against one of the hull-joining edges (with the grain so positioned that both joining edges are on a plane perpendicular to the impact band), then the two shells of the Hull will separate along the joining edges, as along these joining edges are where the least resistant parts of the Hull are located.
Further, in the decorticator of the present invention, one of the joining edges of the Hulls (the one opposite the impacting edge) is abraded against the hardened steel of the rotor channels, which weakens the joint and facilitates decorticating, as will be later explained.
Consequently, if a high energy lateral impact is achieved along one of these lines of fracture, the two Hull shells shall open, freeing the Kernel from inside and, through this decorticating action, making possible the later separation of Kernels from Hulls.